Floor treatment machines for polishing, grinding, sanding or otherwise treating surfaces such as concrete or wood floors are well known. U.S. Pat. No. 5,514,027, describes an example of such a floor treatment machine. The floor treatment machine has a handle and a housing containing a motor that rotates a floor treatment head.
In use, the head of the machine rotates on the floor surface that is being treated. The head has twelve pin-type abraders mounted to a disk. When the disk rotates, the abraders sand the surface of the floor. However, the disk can abruptly stop if the abraders contact an obstruction, such as a protrusion on an uneven floor. In stopping abruptly, a torque is applied to the linkage between the motor and the stationary head. This torque can break the linkage or otherwise damage the motor of the floor treatment machine.
U.S. Pat. No. 2,785,424 describes another floor treatment machine that has a centrifugal clutch. While the clutch of this machine is generally effective and is intended to allow the machine's motor to remain spinning when the machine's head hits an obstruction, it has certain drawbacks. In particular, as described at column 9, line 50, the centrifugal clutch is relatively complicated and therefore can be less reliable and more expensive to manufacture and to maintain.
Accordingly, there exists a need for a floor treatment machine with a torque overload protection device that is reliable and inexpensive to manufacture. The present invention solves these problems and provides further related advantages.